1. Field of the Invention
This invention relates to a feeding device to feed, sheet by sheet, a plurality of stacked sheets of paper cut in a predetermined size into an image forming apparatus such as, for example, a reproduction apparatus, printing machine, and so forth. More particularly, it is concerned with a paper feeding device to feed, sheet by sheet, a plurality of stacked sheets of paper cut in a predetermined size by use of pawls serving to separate such stacked sheets on a stacking table.
2. Description of the Prior Art
As a device for separating and feeding, sheet by sheet, a plurality of sheets of paper cut in size and stacked on a stacking table, there has so far been widely used a device of such a construction, wherein a set of separation pawls are urged against the forward end corners of the stack of cut sheets, and feeding rollers are press-contacted on the surface of the top sheet, while they are being rotated, thereby forming warp in the top sheet between the separation pawls and the feeding rollers, and causing the top sheet alone to be released from the separation pawls.
Such conventional feeding device, however, has various problem to be mentioned hereinbelow in reference to Figures of drawing accompanied by this application.
Referring to FIGS. 1 and 2, respectively showing a side elevational view and a top plan view of the conventional feeding device, a pile of sheets of paper P cut in a predetermined size are placed on a stacking table 1, the topmost sheet press-contacting to feeding rollers 3, 3a by force of a spring 4. By rotation of the feeding rollers 3, 3a in the direction of an arrow in the drawing, the topmost sheet is advanced by frictional force with the feeding rollers 3, 3a. At this instant, warps A, B are formed in the top sheet between its forward end corners and the feeding rollers 3, 3a due to separation pawls 5, 5a. The warping causes the sheet to be separated from other stacked sheets, released from the separation pawls due to restoring force which tends to reinstate the paper to its original flat state from its warped condition, and fed out. By the way, a reference numeral 6 designates a pivotal point for oscillation of the stacking table 1.
FIG. 3 illustrates a state of the warp B which has been formed under the optimum condition of a distance from the feeding roller 3a to the separation pawl 5a, wherein the topmost sheet is in a state of being slightly pushed forward, and the warped corner B is about to be released from the separation pawl 5a due to the restoring force of the sheet. Here, when cut sheets having the same paper width are to be fed by the same feeding device, the feed rollers can be disposed at an equal and optimum distance from the left and right separation pawls, as shown in FIG. 2. However, in case the cut sheets in various sizes are required to be fed into reproduction apparatus, etc. by the same feeding device, it is difficult to fixedly maintain the feed rollers at such equal and optimum distance from the left and right separation pawls. For instance, when the feed rollers 3, 3a are disposed at the optimum positions suited for a paper width L.sub.0 as in FIG. 4, such positioning will not do for a sheet having a width L.sub.1, because, in this case, the feed roller 3a is on one edge of the sheet, on account of which no warp is formed at this position. This would cause an inbalanced condition in the sheet feeding at both left and right sides. Also, with a sheet having a width L.sub.2, since the feed roller 3a is too distant from the separation pawl 5a, the warp B becomes excessively large to reduce the restoring force of the sheet, whereby it becomes difficult for the sheet to be released from the separation pawl 5a. This would also cause an inbalanced condition in the sheet feeding at both left and right sides.